Method of making bifocal lenses.



F. A. STEVENS. METHOD OF MAKING BIPOGAL LENSES.

APPLICATION FILED MAR.2,1908.

9 Patented 0011.20, 1908.

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UNITED STATES FREDERICK A. STEVENS, OF PROVIDENCE, RHODE ISLAN-PATENTLOFFICE METHOD OF MAKING BIFOGAL LENSES.

Application filed March 2, 1908. Serial No. 418,704

Specification of Letters Patent.

" Patented. eta-1 20, eos.

the following is a specification.

My invention relates to methods of uniting glass blanks, and isarticularly adapted to the manufacture of bi-focal lenses.

Heretofore, it has been customary to grind and fit the face of one orboth blanks preparatory to uniting, and either cement or fuse one ofthese blanks into the ground surface of the other. The labor, skill, andexpense involved in the grinding method is excessive; and the variety insurface and sectional contour of the embedded member is limited.

To the end essentially of overcoming the enumerated disadvantages, myinvention consists in the steps and operationshereinafter set forth andpointed out in the claims.

In the accompanying drawings which constitute a part of thisspecification, Figure 1 is a plan view of a device or apparatus in conjunction with which my process may be carried out, supporting twosuperimposed glass blanks intended to be operated upon. Fig. 2 is asection on line m as of Fig. '1. Fig. 3, a like section of the arts at asucceeding stage of construction. ig. 4, a similar section of thecompleted product. Fig. 5, a section of a modified form of die takenupon the section indicated in Fig. 1. v Fig. 6, a like section ofanother modified form of die and superimposed parts after the fusingprocess, and Fig. 7, a similar section of the completed product made inconjunction with the modified form of die shown in Fig. 6.

Like reference characters indicate like parts throughout the views.

My process is illustrated in this instance as performed upon two blanksintended for use in the construction of bi-focal lenses. In connectionwith my process, in this instance, is provided a metal block or die, A,provided in its upper face with a cavity, a, shown in Figs. 2 and 3, asconcave, from whose lowest oint is a vertical duct, B, extending into aarger openin C, which receives the end of a pipe, D, leac ing to an airpump, E. A portion of the pipe, D, isshown broken'away in" Figs. 2, 3, 5and 6. In Fig. 5, a plurality of ducts, B, are shown. In connection withthe production of prismatic effects the form of die cavity, a, asshown-in Fig. 5, is desirable. In short, as will be later evident, thedie cavity, a, may be annular or ofany desired outline best adaptedtouse-in any par ticular class of work; furthermore, the number of the diecavities may be increased when desired, as in the case of'themanufacture of lenses having more; than two foe-1 The block, A,referablyirestsina muflier, or has suflicient eat appliedthereto in anyconvenient manner to moderatel raise its temperature. Y 1. My rocess,when? or 0 ed in con'unction wlth the describe. do es, is as follows:The two glass blanks, F and-G, intended for treatment are assembled oneupon the other. The blank, G, being the u per. of the two. In this case,F re resents a ens blank, and G a smaller or auxi iary blank restingthereon, having a refractive index differing from that of blank, F, andfusible at a lower degree of temperature than the latter. It is somebefore being operated upon; in which case the temperature of the blanksmay be raised sufficiently to fuse their contacting surfaces. It isreferable, but not essential, that the blanks e allowed to cool beforeproceeding. The blanks thus assembled, with blank F below blank G, aresubjected to sufplaced upon the block, A, whereupon the air is exhaustedby pump, E, from the cavity, a, through the duct, B, and pipe, D,thereby forcing by atmospheric pressure or suction the compound blankdown into the cavity as shown in Figs. 3 and 6. After cooling, theblanks thus welded are removed and their project-ing up er and lowerfaces ground to complete the esired lens.

What I claim is,

1. The method of uniting lens bla'nkswvhich consists in assembling theblanks one upon the other, rendering the assembled blanks plastic bysubjecting them to heat, and bending the blanks transversely byatmospheric pressure.

2. The method of uniting lens blanks which consists in assembling blanksof different refractive indices one above the other, rendering theassembled blanks plastic by subjecting them to heat, and transverselybending the plastic blanks by atmos heric pressure.

3. The method of uniting ens blanks which consists in assembling theblanks one upon the other, subjecting the blanks to heat to ficient heatto render both blanks plastic, and

times desirable to unite the assembled blanks fuse together theircontacting surfaces, reducing the united blanks to a plastic conditionby heat, and bending the blanks transversely by atmospheric pressure.

4. The method of uniting lens blanks which consists in assembling blanksof different refractive indices one upon the other, subjecting theblanks to heat to fuse together their contacting surfaces, reducing theunited blanks to a plastic condition by heat, and bending the blankstransversely by atmospheric pressure.

The method of uniting lens blanks which T upon adie provided with acavity beneath the blanks, and exhausting the air from the consists inassembling blanks one upon the other, the upper blank being fusible at alower temperature than the lower blank, sub- "the cavity.

jecting the blanks to heat sufficient to fuse the face of the upperblank to the face of the lower blank, reducing the united blanks to aplastic condition by heat, and bending the blanks transversely byatmospheric pressure.

6. The method of uniting lens blanks which consists in assembling blanksof different refractive indiccs one n 3011 the. other, the upper blankbeing fusible at a lower degree of temperature than the lower blank,subjecting the blanks to heat to fuse the upper blank to the lowerblank, reducing the united blanks to a plastic condition by heat, andbending the blanks transversely by atmospheric pressure.

7. The method of uniting lens blanks which consists in superimposing oneblank upon the other, reducing the blanks to a plastic condition byheat, placing the plastic blanks upon a die provided with a cavitybeneath the blanks, and exhausting the air from the cavity to force thematerial of the blanks into the cavity.

S. The method of uniting lens blanks which consists in assembling theblanks one upon the other, subj ccting the assembled blanks to heat tofuse together their contacting surfaces, reducing the united blanks to aplastic condition by heat, placing the plastic blanks cavity to forcethe ma-teria-l of the blanks into 9. The inethod of uniting lens blankswhich consists in fixing in any convenient manner one lens blank uponanother, placing the blanks upon a die provided with a cavity beneaththe blanks, subjecting the blanks so positioned to heat to render thesame plastic, and exhausting the. air from the cavity to force thematerial of the blanks into the cavity.

In testimony whereof I have aliixed my signature in presence of twowitnesses.

FREDERICK A. S'IEVENS. Witnesses:

l'IORATIO E. BELLows, JosnPn E. BnRNs.

